Condenser transmitter apparatus



Jan. 27, 1931. J. E. JENKINS ETAL CONDENSER TRANSMITTER APPARATUS FiledJuly so, 1928 2 Sheets-Sheet 1 Jan. 27, 1931. j I J. E. JENKINS E AL1,790,505

CONDENSER TRANSMI TTER APPARATUS Filed July 30, 1928 2 Sheets$heet 2Patented 27, 1931 NDENBEJR TRANQMITTEE P Application filed July t0,

@ur invention relates to transmitter apparatus and particularly toapparatus for use in connection with sound pick-up devices of thecondenser type used for broadcasting t purposes.

ln using condenser type transmitters and instruments of like nature, itis desirable to have the electrical conductors extending between thetransmitter and the amplifier as short as possible in order to increasethe operating eficiency of the transmitter and to this end, the presentinvention provides a durable, practical and conveniently arranged devicefor supporting a transmitter, said device being designed to support atransmitter in juxtaposition with respect to an amplifying unit, wherebythe length of the connecting leads or conductors will be reduced to aminimum.

it is also an object of our invention to provide a transmitter device ofthe instant nature which comprises a very compactly arranged amplifyingunit which is self con tained and readily accessible or removable forpurposes of repair or replacement, from a suitable housing withoutdisturbing the po sition of a sound pick-up unit or transmitlersupported by said housing.

A still further object of the present invention is to'provide a supportwhich includes a trams or casing for resiliently supporting atransmitter and a resilient clamping band in which the transmitter maybe detachably supported, this clamping band serving as a very convenientmeans to permit the associa tion or disassociation of the transmitterwithout requiring the'dismantling of any of the supporting elements.

Uur invention further contemplates the provision of a transmittersupport which includes a plurality of radially positioned nonmetallicresilient members, said members being secured to a mounting at theirouter extremities, the inner extremities thereof being associated withthe transmitter unit, said members being of such a construction as toprevent the introduction of interfering, humming noises which haveheretofore been occasioned when metallic springs and the like r orcnrcaeo, minors, assrenons 'ro monitors, a nna'rron or ILLmoIs eTUs1928. Serial N0. 29$,Q5Q.

have beenemployed to support the usual carbon type transmitters.

In addition to the above mentioned advantageous characteristics, ourinvention contemplates the provision of an economical and durablecondenser traitter supporting device in which the efl'ectiveness of theoutput is greatly enhanced b reason of the fact that the shortness ofthe eads which connect the transmitter and the amplifier reduces theinactive capacity to a minimum, and conductors which are adapted to beconnected to the output and battery terminals, are compactly arranged.-so as to presenta flexible cable, said conductors being provided with ametallic sheathing which serves as a shield against the introduction ofnoises resulting from external influences to which the cable mag besubjected. v

still further object of this invention is to provide an amplifier casingof rigid con struction and pleasing appearance which is designed tosupport a transmitter and which is further adapted for convenientattachment to conventional types of microphone stands, said casing beingalso designed to rest upon a fiat surface in instances where microphonestands can not be conveniently used.

Another and more specific object of our invention is to provide acondenser transmitter for broadcasting, honograph recording and otherpower spea ing systems which comprises an amplifier housing andtransmitter support of attractive design and adapted for convenientassociation with 1 conventional microphone stands, said housinghaving'an open back portion which exposes the elements comprising theamplifier when a housing cover is removed, thereby greatl facilitatingthe repairing or replacement 0 said amplifier elements.

These and other objects will be more ap-v parent from the followingdetailed descri tion when considered in connection with t e accompanyingdrawings wherein:

Figure 1 is a front elevational View of a transmitter device which isrepresentative of I Figure 2 is a side elevational view of the deviceshown in Figure 1;

Figure 3 is a rear View of the transmitter device as viewed along theline 3-3 of Figure 2;

Figure 4 is a vertical central sectional view taken substantially on theline 4-4 of Figure 3, certain of the elements such as t e vacuum tubeand the transmitter proper bein shown in elevation;

igure 5 is a detailed front elevational view of the improved transmitterclamping P igure 6 is a fragmentary View of the improved cable which isprovided with metallic sheathing for electrically shielding theconductors which comprise said cable; and

Figure 7 is an enlarged transverse sectional view of the cable takenalong the line 77 of Figure 6.

Referring now to the drawings wherein like numerals have been employedto designate similar parts throughout the various figures, it will beobserved that one embodiment of our invention resides in a casing orframe member 2 of box-like design which is adapted to be open at theback thereof by the removal of a cover member 4. This cover member 4 isremovably secured to the casing by means of suitable thumb screws 6. Thecasing 2 and the cover 4 serve to efiectively house or enclose acompactly arranged amplifying unit indicated generally by the numeral 8,Figures 3 and 4 and the elements constituting this amplifying unit suchas the vacuum tube 10, the terminal supporting bar 12 and other elementswhich need not be specifically set forth, are self-contained within arectangular frame 14. This frame 14 provides a convenient mounting forthe ampli- P fier parts and is resiliently secured or floated within thecasing by means of pads 16 constructed of sponge rubber or materialhaving similar resilient characteristics, said pads being interposedbetween the casing walls and the frame 14. These pads are preferablycemented to the inner surfaces of the casing walls and permit theamplifying unit 8 contained within the frame 14 to be readily withdrawnfrom the casing when the cover 4 has been removed.

Extending outwardly from the front side of the casing 2 are fourequally-spaced support arms 18, the outer extremities of which areprovided with suitable screws 20. These screws 20 are designed toreceive one of the extremities of resilient non-metallic members 22, theopposite extremities of said re-- silient members being connected to eyehooks 24 mounted upon the peripheral surface of a split clamping ring26. This resilient clamping ring 26 is adapted to receive a microphoneunit 28 of the condenser type and a non-metallic resilient member 30,Figure 1, extending between adjacent eye hooks 24 across the splitportion of said ring, cooperates with the inherent resiliency of thering to cause the microphone 28 to be securely clamped in position; Itwill be observed that by employing our simple split ring structure thetransmitter unit 28 may be expeditiously associated with anddisassociated from the resilient supporting members 22 withoutnecessitating the dismantling or rearrangement of the members 22. Thisis to be clearly distinguished from microphone supporting devices whichhave heretofore been employed wherein considerable time and effort mustbe expended in order to remove or replace the microphone or transmitterunit. In this connection it is also to be understood that we prefer toemloy non-metallic resilient supporting memers such as members .22 inorder to positively preclude the introduction of undesirable humming orsinging noises which are occasioned when metallic structure such as coilsprings and the like are'used as-a supporting medium. The lower portionof the clamping ring 28 is provided with a socket 32, Figures 2, 4 and 5which is designed to slidably receive a companion terminal plu 34 whichforms the terminal of a groun wire 36. The transmitter 28 iselectrically connected with the amplifier unit 28 through the medium ofa conductor 38 which is provided with a plug 40, Figure 4, at oneterminal thereof, said terminal being designed for removable insertioncentrally of the transmitter 28. The opposite extremity of theconductor38 is suitably connected to the operative circuit of the amplifier unitand likewise the opposite terminal of the ground wire 36 is connected toa suitable binding 0st 42, Figure 3, mounted upon the lower side of theframe 14. From the foregoing it will be apparent that the plug andsocket arrangement just described, together with the resilient clampingring 26, renders the amplifying unit 8 readily removable from the casing2 without the necessity of disturbing the position of the transmitterunit or any of the supporting elements associated therewith. Likewisethe transmitter unit may be readily removed from the resilient clampingring 26 and disconnected from the ground wire 36 and the conductor 38with little effort and without necessitating the rearrangement of any ofthe transmitter parts. By having the condenser transmitter 28juxtapositioned with respect to the amplifier unit 8, the connectingleads, namely the ground wire 36 and the conductor 38, will obviouslyvery short By having these wires of minimum length, the effectivevariation in capacity of the condenser at voice frequencies is obtainedand by employing a transmitter of our construction the output resistanceis reduced to a minimum.

It will be observed that the terminal supiii) portingbar 12 isvertically positioned within the frame M and is designed to support aplurality of terminals or binding posts for the conductors whichcomprise a cable at. Three of these binding posts may be connected tobattery through suitable conductors 46, t8 and 50, Figures 3, 6 and 7,and the other two binding posts may be connected with out-put conductors52 and 54. In order to prevent the introduction of noises which mightresult from conditions surrounding the conductors, we apply a metallicsheathing 56 upon the output conductors 52 and 54:

and another metallic sheathing 58 around the entire group of conductors,as clearly shown in Figures 8 and 7 which contacts with the shield orsheathing 56 throughout its entire length. An insulating fabric covering60 is applied to the outer surface of the metallic sheathing 58.

It will be observed that the sheathings 56 and 58 are preferablybraided, thereby rendering the cable suciently flexible to meet theneeds incident to its use. By having the conductors shielded by thesemetallic sheathings in the manner shown, the operating efficiency of thedescribed apparatus is materially increased by reason of the fact thatthe quiet operation thereof is insured, ln other words, externaldisturbing influences to which the cable may be subjected are renderedined'ective by reason of the shield 58 and the shield 56 protects theoutput con ductors against disturbing efiects of the cur- :ent flowwithin the battery conductors. it will be observed that the cable 44passes through an insulating collar 62 which is mounted within thebottom wall of the casing 2, and this collar has a sliding fit within agroove in the casing, thereby rendering the collar readily removablealter the cover 4 has been removed. ln order to properly connect the.metallic sheathing 56 and 58 to ground, an extended portion of thesheathing 56, Figure 3, is provided which is suitably connected to theground terminal or binding post 42. In order to efiectively connect themetallic frame it to ground, a resilient contact finger 68, Figure 3, issecured to the side of the frame 14: and is adapted to resilientlyengage the inner surface of the casing 2. it will also be apparent thatcontact between the sheathing 58 and 58 may be etlected other than bymaking contact throughout the entire length thereof.

The entire transmitter device is ada ted tor attachment to aconventional type 0 microphone stand indicated generally by the numeral68. This stand 68 includesan upright stem or rod 70 which is designed todetachably receive a ring type supporting member 72. A. plurality of eyehooks 74 equally spaced along the inner periphery of the ring member 72are adapted to be clamped against projections 76, Figures 2 and 4, whichextend outwardly and are formed integral with the casing '2. Convenientmeans such as thumb screws 78 may be employed to clamp these eye hooks74 a ainst the projections 76. The transmitter evioe is thus adapted tobe conveniently mounted and well balanced at the upper extremity of themicrophone stand and in instances where it is not convenient to employan upright microphone stand, supporting members or feet 80 formed at thelower portion of the casing 2 provide convenient means to enable thetransmitter device to be placed upon a flat surface such as a desk ortable.

From the foregoing description it will be understood that our inventionprovides a portable transmitter device which is not only ornamental inappearance, but which is also of a very practical construction. Byhaving the condenser transmitter unit juxtapositioned with respect tothe amplifier unit, the length of the connecting conductors is reducedto a minimum and by having said amplifier unit self-contained within aframe, and detachably mounted within-a casing, the ease with whichreplacement, repairs and the like may be made is greatly facilitated. Itis also to be understood that the non-metallic resilient members whichsupport the microphone unit will not cause an noises to be introducedwithin the microp one in response to the jarring or inadvertentdisplacement thereof. As already suggested, this construction should bedistinguished from the use of metallic supports which might introducenoises in response to the springing or flexing thereof. By employing ourimproved annular clamping device for securing the transmitter unit inposition, said unit may be removed or inserted without the necessity ofrearranging or disassembling any of the transmitter supporting elements.It will further be appreciated that an advantageous characteristic of atransmitter device produced in accordance with the teachings of ourinvention resides in the use of shielded conductors which are connectedwith the amplifier unit. lhe metallic braided sheathing materialincluded within the flexible cable serves very efiectively to eliminatethe introduction of disturbing noises, which might otherwise beintroduced as the result of conditions surrounding said conductors. inad dition to the above mentioned desirable characteristics, it will bereadily understood that our improved condenser transmitter device may beconveniently mounted upon a conventional microphone stand and is alsodesigned to be placed upon a flat surface such as a desk or table top ininstances where it is more advantageous to have the device thuspositioned. By having the open back arrangement of the transmittercasing, the accessibility to the various parts which constitute theamplifier unit is greatly facilitated and by having the plug and socketconnection between the amplifier leads and the microphone unit, said am;

plifier may be removed from the casing with we claim as new and desireto secure by Letters Patent is:

1. In transmitter apparatus of the class described, a frame forsupportin a condenser type transmitter, a unitary amp ifier support ingmeans adapted to be detachably associated with the frame injuxtaposition with respect to a supported transmitter without thenecessity of isturbing the position of said transmitter and a completeamplifier unit on said supporting means.

2. In transmitter apparatus of the class described, a frame, a resilientclampin ring adapted to yieldingly engage the sur ace of a transmitterunit and means carried by the frame for properly supporting the clampingrin 3% In combinationwith an amplifier unit having relatively shortleads adapted to make a sliding contact with condenser type transmitter,a frame adapted to render the amplifier unit substantially selfcontained, a

housing for said frame having an open back portion to permit of theconvenient association and disassociation of the frame with respect tothe housing, and means carried by the housing for supporting atransmitter in juxtaposition with respect to' the housed amplifier unit.

4. In transmitter apparatus of the class described, a frame forsupporting an amplifier unit, means for supporting a condenser.

transmitter adjacent to a supported amplifying unit, and a plurality ofadjacently positioned output and battery electrical conductors extendingfrom the amplifier frame'having metallic sheathing for electricallyshielding the individual adjacently positioned conductors.

5. In combination with an amplifier unit and an adjacently positionedtransmitter connected thereto, a plurality of compactly arranged batteryand output conductors, and a metallic sheathing enclosing and separatingcertain of said conductors to protect against the introduction of sounddisturbances.

6. In combination with an amplifier unit and an adjacently connectedtransmitter, a

plurality of compactly arranged battery and output electricalconductors, a flexible metallic sheathing surrounding the outputconductors to electrically protect against disturbing effects from thecurrent flow within the battery conductors, and another flexiblemetallic sheathing surrounding the battery H conductors and havingcontact with the first mentioned sheathing to further protect theconductors as a shield against the introduction of sound disturbancesfrom external influences.

8. In transmitter apparatus of the class described, a frame forsupporting an amplifier unit, a housing therefor, said housing beingdesigned to support a transmitter unit, and means provided on saidhousing for securing the same to an upright elongated transmitter stand,said housing being also designed to be positioned upon a fiat surface,in lieu of the association thereof with an upright trans-- mitter stand.p

9. In transmitter apparatus of the class described, a frame forsupporting an amplifier unit, a housing for detachably receiving theamplifier unit supported by the frame, a removable cover at the backportion of the housing, means on the front portion of the housing forsupporting a transmitter unit, and means for securing the housing to thetop of an upright stand.

10. In a transmitter apparatus of the class described, a frame forcompactly supporting a complete amplifier unit, a box-like housingadapted to detachably receive said amplifier frame, a substantiallycomplete amplifier described, a housing, a frame detachably mountedWithin said housing, a substantially complete amplifying unit includinga vacuum tube, transformer, condenser and conlift ductors housed withinsaid frame and movable therewlth as a unit, whereby said completeamplifier unit may be readily attached or detached with respect to saidhousing, and a transmitter unit supported by said housa substantiallycomplete amplifier unit in eluding. a vacuum tube, transformer,condenser'and conductors mounted within the walls of said frame, wherebysaid amplifier unit may be moved with the frame as a selfcontained unit,a cover on said housing adapted when open, to expose the open portion ofthe amplifier supporting frame and thereby rerider the amplifierelement-s readily accessible, and a transmitter unit supported by saidhousing in juxta-pos'ition with respect to said amplifier unit.

13. In transmitter apparatus of the class described, a frame, an annularmember hav ing a smooth inner surface. a cylindrical transmitter unithaving a smooth peripheral surface adapted to make a sliding fit withinsaid annular member whereby said parts may be connected by impartingrelative axial movement thereto, and supporting means extending betweenthe frame and the annular member. 7

14. In transmitter apparatus of the class described, a frame, said framehaving an internal annular surface associated therewith for slidablyreceiving a cylindrical transmitter unit, and a transmitter unit havinga cylindrical surface adapted to make a sliding fit with said internalannular surface, whereby said parts may be connected by impartingrelative axial and rotative movement thereto.

15. In transmitter apparatus of the class described, a housing, adetachable frame within said housing, an amplifier unit mounted in saidframe, a condenser transmitter unit supported by said housing andpositioned adjacent said amplifier unit, and meansfor electricallyconnecting said condenser transmitter unit and said amplifier unit, saidconnection being such as to enable. the disconnection of the transmitterunit from the amplifier unit by manually urging ing a cylindricalsurface adapted to make a sliding fit within a companion internalcylindrical annular surface, and an electrical'conn'ection between saidtransmitter unit and said amplifier unit, said transmitter unit be ingadapted when urged axiallv away from the amplifier unit to becomeautomatically disconnected therefrom;

17. In transmitter apparatus of the class described, a housing, one-sideof said housing being; open to detachably receive an amplifier unit, aortion of said housing oppositely disposed from said opening beingadapted to support a condenser type transmitter, a condenser typetransmitter su ported by said housing, a frame detachab y mounted insaid housin adjacent said supported transmitter, a su ntially completeamplifier unit carried by said frame, and electrical connections betweensaid transmitter unit and said amplifier unit.

18. In transmitter apparatus of the class described, a-housing, acondenser type trans-- mitter supported on one'side of said housing, acover member on the opposite side of said housing which is adapted whenopen to enable the association within the housing of an amplifier unit,a frame, and a substantially complete amplifier unit carried by saidframe, said frame being detachably mounted within the housing betweensaid transmitter unit and said cover member. a

19. In transmitter apparatus of the class described, a housin a supportdetachably mounted within sai housing, amplifier elements such as vacuumtubes. carried by said support and movable therewith as a unit,wherebythe amplifier elements carried by the support may be readilyattached or detached with respect to said housing, and a transmitterunit supported by said housin in juxtaposition with respect to the houseamplifier unit. i

20. In transmitter apparatus of the class described, a housing, one sideof said housing being open to detachably receive amplifier elements, aportion of said housing oppositely disposed from said opening beingadapted to support a condenser type transmitter, a condenser typetransmitter supported by said housing, a carrier detachably mountedwithin said housing adjacent said supported transmitter, amplifierelements mounted on said carrier, and electrical connectionsbetween saidtransmitter unit and said amplifier elements.

In testimony whereof, we have hereunto subscribed our names.

JOHN ELLIOTT JENKINS. SAMUEL E. ADAIR.

